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Question:

aranna3028
aranna3028
Student
High School - 9th Grade

I need the explanation how to solve this:

A) 45 - 2x when x = 6

B)12 - 2x2 + 5x when x = -4

C)(x + 7)(x - 2) when x = -5

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Posted by aranna3028 on Monday May 25, 2009 at 5:04 PM and tagged with math.

Answers:

  1. neela
    neela Teacher
    Graduate School

    eNotes Editor

    A) Let f(x) = 45-2x . When x=6.Put x=6 in f(x) .f(6)= 45-2(6) = 45-2*6 =45-12 = 33

    B) Let g(x)=12-2x^2 +5x    (1) , when x=-4.Substiting x= -4 in g(x), we get g(-4) = 12-2(-4)^2  +5(-4) = 12-2*16-20  = -40.

    C) Let f(x)= (x+7)(x-2) when x=-5. Putting x=-5 in  f(x) =(x+7)(x-2), we get f(-5) = (-5+7)(-5-2) = 2*(-7) =-14

     

     

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    Posted by neela on Monday May 25, 2009 at 8:31 PM


  2. catlover Student
    High School - 10th Grade

    Well, first of all, for A u should plug in the value x into the equation (which is 6) So, your equation should look like this

    45-2(6) Now, just do your order of operations, or in other words, multiply 2 by 6 which equals 12. Then your equation will be 45-12. Just subtract this and your answer for A is 33.

    As for C, plug in your values for x (which is -5) Your equation should be (-5+7)(-5-2). Now, solve the equations within your parentheses first. -5+7=2 and -5-2=-7 Your new equation should be (2)(-7) and when u multiply these together, your answer is -14.

    Hope this helps!!

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    Posted by catlover on Tuesday May 26, 2009 at 4:22 PM